The invention is directed generally to a method and apparatus for determining energy usage at a plurality of locations served by a common energy source and allocating the costs of the energy so used accordingly. More specifically, the application is directed to the problem of arriving at an equitable allocation among various tenants of a building of the total heating costs for the building.
In both commercial and residential structures, tenants often control the temperatures of their individual units. However, such multiple-unit structures often have but a single unified heating system serving all units. With energy costs continually increasing, building owners, condominium associations, and the like have become increasingly concerned over the costs of heating. For example, some tenants or unit owners may consume considerably more heat energy than others, whereby equal division of the costs among all owners, in the form of rental increases or maintenance assessments is inequitable.
Accordingly, it is desirable to provide an equitable means of allocating costs of heat energy in accordance with individual tenant's consumption of heat energy. As an additional benefit, it is believed that as individual tenants become aware of the cost of heat energy consumption attributable to them, they will take steps to conserve or control energy usage.
One system has heretofore been proposed, wherein individual meters are installed for each tenant's unit. These meters respond to the tenant's thermostat calling for heat and to the temperature at a given location, such as the hot water in a heating system pipe leading to or from that unit, exceeding a certain level for actuating the meter. Thereupon, the meter records time proportionate units until either the thermostat deactivates or the monitored temperature again drops below a given level.
The foregoing system requires, however, that each unit be visited to set or calibrate the meters and to record the meter reading at periodic intervals, in order to arrive at a cost allocation. Moreover, it has been found that other variables may require a variation or adjustment in the temperature setting at which meter operation is initiated. In the foregoing prior art system, the need for such a change may not become apparent until comparison of meter readings for similarly situated units reveals discrepancies. Moreover, such a change would again require a visit to the individual unit for adjustment, repair or replacement of the temperature monitoring components.
Additionally, the foregoing prior art system makes no provision for detecting other possible malfunctions in the heating system itself or in the individual metering systems. Hence, only careful comparison of successive readings to reveal any discrepancies would generally reveal such malfunctions.
Moreover, it has been found that cost allocation based upon such a meter reading alone may not achieve equitable results. For example, in a given building, some units may consume more energy than other units of the same size in maintaining the same average temperature levels. This may be due to the relative locations of units with respect to outside walls, common walls, and the like. Similarly, outside walls carrying differing numbers of windows and having different directions of exposure (north, south, etc.), may effect heat requirements. Many other physical factors including the construction of the building and location of units may affect heat energy requirements.
Hence, it is desirable to take into account the differing energy requirements of each unit in carrying out the cost allocation process, and updating the parameters monitored by the system.